1. Field of the Invention
This invention relates to a vehicle route guidance apparatus for guiding the user through a route using a generated voice and more particularly to researching for a route when the vehicle carrying the apparatus goes off the route.
2. Description of the Related Art
Various types of apparatus to relieve drivers of their work load have been designed and are carried by vehicles. One of them is a route guidance apparatus for guiding the user through a route to a destination. A route guidance apparatus which has a function of informing the driver of routing, when the vehicle passes a branch point such as a crossing, for guiding the driver through the route with a generated voice is known. Such an apparatus it is disclosed, for example, in Japanese Patent Laid-Open No.Hei 1-173815.
When a destination is entered, the route guidance apparatus can search for a route from the current place to the destination and then display the found route for the driver. It also has a function of detecting the current position of the vehicle. When the vehicle moves, the route guidance apparatus displays both the route and the current position for guiding the driver through the route.
On the other hand, although the driver is guided through the route, the vehicle may stray off the predetermined route. In such a case, the driver might want to know a new route from the current place to the destination. Proposed in Japanese Patent Laid-Open No.Hei 1-173815 is an apparatus which, when the vehicle goes off the preset route, alerts the driver and researches for a new route to the destination.
The route guidance apparatus enables the driver to obtain preferred guidance through a new route from the current place to the destination if the vehicle goes off the route.
However, when the driver is on the way to the destination, they may place the vehicle off the route on purpose, perhaps in order to do some shopping at a store along the road or to pick up a person on the assumption that the driver will return the vehicle to the predetermined route. Even in such a case, the conventional apparatus automatically researches for a route. Further, if the driver returns the vehicle to the original route by taking a different route from the researching result, the apparatus repeats researching. While researching is being executed, guidance stops. Unnecessary researching is performed and the operation of the apparatus does not meet the user's needs.